Numerical Analysis On The Propagation Of Subway-induced Tunnel And Soil Vibration And Its Model Parameter Effects

With the rapid development of domestic economy and the expansion of urban scale,urban rail transit has become the first choice to solve the problem of urban traffic congestion.With its advantages of convenience,high efficiency,comfort and safety,and small air pollution,subway has developed rapidly.At the same time,the impact of the vibration induced by the subway operation on the environment has become one of the issues that people pay more and more attention to.Many facts have proved that some subway lines have a great impact on the physical and mental health of human body,the structural safety of tunnel and the normal use of precision instruments,the vibration pollution generated in the subway operation cannot be ignored.It is of great significance for subway construction,vibration reduction and noise reduction design to study the propagation law of ground vibration induced by subway and the vibration response of buildings.The main research contents and conclusions are as follows:1.Using the discrete elastic foundation track beam model to establish a vehicle-track coupling model;consider the six-level irregularity spectrum of the American track,use the periodic graph method to simulate the irregular time series samples,as the input excitation on the track in the model,and then perform dynamics on the model The calculated wheel-rail force provides reliable excitation conditions for further accurate analysis of the vibration response of the surrounding environment caused by the subway.2.Based on the parameters of soil layer and train running speed measured on site in a tunnel section of a subway,the two-dimensional finite element prediction model proposed in this paper was used to calculate the vibration of the tunnel bed and ground environment of the tunnel under the action of single line and double line trains.The analysis and comparative analysis with the measured vibration data in the tunnel of this line verify the accuracy and reliability of the prediction model in this paper.3.The two-dimensional and three-dimensional finite element models of track-tunnel-soil interaction system are established respectively.Considering the influence of soil depth,width,train speed and other factors,the vibration responses of ground measurement points are calculated,and the vibration response results of the two-dimensional and three-dimensional models are compared and analyzed.It is found that the results computed by the 2D and 3D model presented by this paper used to simulate tunnel and soil vibration caused by a subway are reliable,and the calculated vibration of the two-line train is stronger than that of the single-line train.The change of soildepth,width and other size parameters has a certain impact on the ground vibration response.The analysis results show that when the model selected depth is 75 m and the width is120 m,the model calculation results analysis is suitable.In the calculation results of the 2D and 3D vibration models,the impact of ground points caused by subway vibrations gradually decreases with increase of the distance from the center line,the vertical vibration acceleration response of the ground measurement points caused by the train operation will produce the vibration amplification phenomenon near the distance of 23 m from the center line above the subway,due to the repeated reflection of waves in different soft and hard above soil layers.The change of subway train operating speed has a great influence on the vibration of the tunnel surface environment under the action of the train.The peak value of the vertical acceleration in time domain of each measurement point on the ground surface increases with the increase of the train speed,and the response value increases approximately linear with the growth of the train speed.The results of two-dimensional model and three-dimensional model are compared,the three-dimensional model can be better used to simulate the vibration response of a subway.The vibration response value of two-dimensional model is larger than that of three-dimensional model.